1. Field of Invention
This invention generally relates to methods and systems that determine the position and/or velocity of an image-carrying member.
2. Description of Related Art
Electrophotography, a method of copying or printing documents, is performed by exposing an image representation of a desired original image onto a substantially uniformly charged photoreceptor, such as a belt. In response to that image representation, the charged photoreceptor discharges to create a latent image of the desired original image on the photoreceptor""s surface. Developing material, or toner, is then deposited onto the latent image to form a developed image. The developed image is then transferred to a final substrate, such as paper. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of another image.
Color images may be produced by repeating the above process once for each differently colored toner that is used to make a composite color image. For example, in one color imaging process, referred to herein as the Recharge, Expose, and Develop, Image On Image (REaD IOI) process, a charged photoreceptor surface is exposed to an image which represents a first color. The resulting electrostatic latent image is then developed with a first colored toner to form a first color separation image. The charge, expose and develop process is repeated, for example, for a second colored toner, then for a third colored toner, and finally for a fourth colored toner to form second, third and fourth color separation images. The various differently-colored color separation images are placed in superimposed registration with the first developed color separation image so that a desired composite color image results. The composite color image is then transferred and fused onto an image recording substrate or medium.
An alternate type of copying or printing documents utilizes direct marking methods. In this case the inks or toners are directly applied to the image-bearing member. The application may occur by means of ink or toner ejectors that can be selectively actuated by a central image controller. The superposition of the color separations on the image-bearing member occurs in the same manner as it was mentioned above. Likewise, the transfer to paper occurs in the same manner as explained above.
As a further example of color image generation, the individual color separation images can be placed on the image bearing separate from one another. The superposition of the separations can take place on the paper, where they are sequentially transferred.
Registration offsets in a developed image are undesirable because, if the developed image is transferred to a final substrate without adjusting for the registration offsets, the final transferred image will include the registration offsets. That is, each different color separation image will be slightly out of register, or offset, relative to the other color separation images and/or the receiving substrate.
This invention provides a position-determining sensor on an image-carrying member device module to determine the process-direction position of the image-carrying member to provide real time motion information.
This invention separately provides systems and methods that improve the registration between the color separation images.
This invention separately provides systems and methods that control the output of the image data for one or more of the color separation images and that control the position and velocity of the image-carrying member to remove or reduce registration offsets based on determined position and velocity of the image-carrying member.
This invention separately provides a registration controller for an image-forming device that uses the determined position of the image-carrying member to adjust the image data to reduce or eliminate registration offsets.
In one exemplary embodiment of the systems and methods of this invention, a position-determining controller determines the process-direction position of the image-carrying member by detecting a pattern of position-determining marks using a position-determining sensor and by processing the detected data through averaging or correlation to eliminate detection errors.
These and other features and advantages of the systems and methods of this invention are described in or are apparent from the following detailed description of exemplary embodiments of the invention.